Continuous inductive train control system



y 22, 1941-v w. H. REICHARD I CONTINUOUS INDUCTIVE TRAIN CONTROL SYSTEM 2 Sheets-Sheet l Filed Jan. 28, 1939 G .3 $2 2 L 3; 2 B X5 E. 8:. Sim w a m 4 d 1 W i r RNEY.

w. H. REICHARD I 2,250,235 CONTINUOUS INDUCTIVE TRAIN CONTROL SYSTEM Filed Jan. 28, 1939 2 Sheets-Sheet 2 July 22, 1941.

INV NTOR.

,g, ATTORNEY-I Patented July 22, 1941 CONTINUOUS INDUCTIVE TRAIN CONTROL SYSTEM Wade H. Reichard, Rochester, N. Y., assignor to General Railway Signal Company, Rochester,

Application January 28, 1939, Serial No. 253,320

29 Claims.

This invention relates, in general, to train control systems, and has more particular reference to train control systems of the coded continuous inductive type wherein the locomotive equipment is adapted to cooperate equally satisfactorily with two different systems of trackway apparatus.

Situations may arise where locomotives equipped with automatic train control apparatus are required to operate over different sections of the same railroad, or over sections of different railroads, wherein the sections are differently equipped with regard to their trackway circuits and apparatus.

With a view to furnishing locomotive apparatus which will satisfy this requirement, this invention has provided apparatus which responds to coded alternating current of one frequency in the track rails to set up various cab signals, and likewise responds to noncoded alternating current of a different frequency from the first mentioned, to set up various cab signals. The locomotive apparatus is so organized that the major part of the apparatus employed for one type of trackway apparatus, is also employed for responding to the other type of trackway apparatus.

Further objects, purposes and characteristic features of this invention will appear as the description progresses, reference being made to the accompanying drawings showing, solely by way of example, and in no manner whatsoever in a limiting sense, one form which the invention can assume.

In the drawings: The single figure, constituted by partial Figures 1A and 13, each on its own sheet, with the upper long edge of 1A matched to the lower long edge of 1B, represents in a wholly diagrammatic manner, trackway apparatus and car carried apparatus showing one form of this invention.

Referring now to the drawings, and first to the trackway apparatus, there is here rep-resented a stretch of track constituted by two track rails I, separated, by insulating joints 2, into a series of isolated blocks A, B, C, D, E, F and G. Traffic is assumed to be in the direction of the arrow 3. As stated above, the trackway apparatus is of two different kinds, that being associated with the blocks EG being of one kind, and that associated with the blocks A--D being of the other kind, the two different systems being shown in the drawings as separated by a double insulation joint 2 It should be understood, however, that these two systems might occuron two physically separate pieces of track, as for example, one track leaving an interlocking plant for traffic in one direction, and the other track leaving the interlocking plant for traffic in a different direction.

Referring first to the trackway apparatus associated with blocks AD, it should be noted that the circuits involved are substantially the same as disclosed in the Hailes patent, Reissue 19,599, dated June 4, 1935; and accordingly, a very brief explanation should sufiice for the present disclosure.

Since the apparatus associated with each location, that is, each place where the exit end of one block and the entrance end of the adjacent block join, is identical, the various like parts will be identified by like reference characters, with distinguishing exponents, or suffixes.

Considering the location at the exit end of block B, a track battery TB is connected across the track rails at the exit end of block B, together with the secondary of a transformer T2, the leads therefrom to the rails including an adjustable inductance 4 and "an adjustable resistance 5 The primary of transformer T2 is connected, through contact finger 6 of the track relay TRZ (connected across the entrance end of the block C) and at times contact finger 1 of a line relay LRZ, selectively to one of the three coding fingers 8 9 and I0 of a code motor M2. The

code motor M2 is energized through a contact finger H and front point, of 'a motor control relay MCRZ which, in turn, is energized through a contact finger 12 of the track relay 'IRl, to thereby give approach control of the coding so that code is placed on the exit end of a block only upon the entrance of a train into such block.

Each line relay, such as line relay LRZ, is energized through a contact finger, such as I3 and front point, of the track relay 'I'R3, of the block next in advance. A source of alternating current, having a frequency of cycles per second, and derived from a power line, or any other suitable source, is connectable to the code motor M2, and to the heels of the coding fingers 8 9 and I0 through contact finger H and front point. This places coded alternating current of 100 cycles, on the track rails of the exit end of a block, in accordance with traflic conditions ahead as reflected by a line relay and a track relay. As can be seen, these relays connect the primary of the track transformer, as T2, to the lower finger I0 when both the line and the track relay are up, to the middle finger 9 when the line relay is down and the track relay its track relay TRS is released, to thereby place the 80 code on the exit end of the block next to the rear of the occupied block upon a train entering such block. In a similar manner, 1220 code is placed on block B, and 180 code is placed on block A, and on all blocks to the rear thereof. In other words, due to the shunting action of the Wheels and axles of a train occupying a block, there is no code to the rear of a train in the occupied block, there is 80 cycle code in the block next in the rear of the occupied block, 120 cycle code in the second block to the rear of the occupied block, and 180 code, in all blocks to the rear thereof.

Referring now to the other type or" trackway apparatus employed in this invention, as shown in connection with blocks EG, each block is equipped with a track transformer, as T6, a track battery TB adjustable inductanccs and resistances 3 and 5 and a track relay At the entrance end to each of these blocks, except possibly the first, there is an acknowledging loop, as H which can be constituted by a loop of Wire, or its equivalent, more or less paralleling the rails, and having the same effect upon car carried receivers as do the rails, as will appear more clearly as the description progresses. i

In this type alternating current of a frequency different from the 100 cycle current employed in the first trackway circuits, is employed, as for example, 140 cycles per second. A source of such current is connected across the primary of the transformer T5, in series with contact finger B8 and front point of the track relay Always connected across the 140 cycle source, at each location, is the acknowledging loop, by way of wires E9 and 29 In this way the supply of 1st cycle alternating current to the acknowledging loops is not ever interrupted by traiiic conditions ahead, but is contemplated as always being present. The supply of 140 cycle alternating current to the exit end of a particular block, by Way of the transformer, as T5, is dependent upon the con- Clition of the block next in advance, and if occupied, its track relay as TRE will be in released position and no alternating current will be present in the block to the rear. If, however, the block immediately in advance of a block in question is not occupied, then 140 cycle alternating current is steadily applied to the exit end of this block in question.

At the place where the first system of trackway circuits, and the second system or" trackway circuits, join, that is, at the double insulating joint 2 the control for the first system is extended, by means of line relay LRt, relays NCR E and M4, contact finger 2%, etc. If the two systems should be separated by an interlocking plant, or otherwise spaced, this additional trackway equipment Would not be necessary to give full protection, since one system would terminate with block D, and there could be no possibility of a train, operating through block I), of becoming endangered by a train occupying block E, which is the first block of the second, or what can be characterized as non-coded, type of trackway apparatus.

Coming now to the car carried apparatus ex-- emplifying the present invention, on each equipped locomotive is a set of receiving coils 22, carried on cores 23, and mounted in front of the first pair of wheels and axle, and positioned with respect to the track rails, so as to be inductively affected by alternating current, or pulsating current, in the track rails whereby a voltage of induction is produced therein. The two coils 22 are connected in series, in a manner to have their induced voltages cumulative, and are connected, by wires 2t and 25, to the primary or" a main transformer MT, through series tuning condensers 26, El, 28 and 29, with a condenser t9 bridged across the connection.

The secondary of the main transformer MT, has bridged across it the tuning condensers 3i and. (i2, and in series therewith is a resistance 33, and this secondary is arranged to impress its voltage, in series with a limiting resistance 34, on the grid 35, of a first tube 36, of any usual three element detecting and amplifying electron tube. The filament 3i, of this tube, and 33, of a second like tube 39, are connected in series, through a suitable resistance 46, to a 32 volt source of direct current. The plate circuit, including plate ii, of the first tube 36, is connected in series with the primary d3, of a transformer M, to a 320 volt source of direct current, by means: of wires 25 and The sec ondary ll of transformer it, is connected in series with a direct current blocking condenser 58, to the grid 39, of the second tube 33, whereby the pulsating voltage in the plate circuit of the first tube is impressed on the grid of the second tube, but the relatively high voltage direct current component is shielded from the grid of the second tube, by the blocking condenser 8.

The plate 56, of the second tube 39, is connected to the primary 5!, of a transformer 52, the secondary 53 of which is connected to a rectifier 5d, of the full-wave type, the out-put side or" rectifier being connected to a code relay CR.

The grid d8 of the second tube, is protected against carrying a Voltage too high for proper functioning of the tube, by means of a grid leak, including a resistance and a condenser 58, connected to ground 5?.

With the apparatus as described just above, each series of alternating current cycles of current flowing in the track rails or in the acknowledging loops, produces induced voltages in the wires 2% and 25 leading to the main transformer MT. With the parts as above described and as shown in the drawings, the receiving circuits to the tubes are tuned to resonance, or substantially so, at cycles per second. Accordingly, the 100 cycle current in the track rails, produces voltages which make the grid 35 of the first tube 38, alternately more and less positive, whereby to vary the magnitude of the plate current of the first tube, and by way of transformer i i, to produce changes in voltage impressed upon the grid 59 of the second tube t t. This pulsating voltage impressed on the grid of the second tube will produce a pulsating direct current in the primary of transformer 52, which, on passing through the transformer, and

the full-wave rectifier 54, will cause direct current to flow through the iCOdG relay CR.

Thus, code relay CR will pick up shortly after alternating current of 100 cycles is placed on the track rails and will release shortly after it is removed therefrom. In this fashion, relay CR will follow the code placed on the track rails by the code motors M, and will pick up and release once for each code cycle. In other words, relay CR will either be in released position, if the receiving train be in an occupied block, or, if not, it will oscillate at a rate of 80, 120 or 180 oscillations per minute, in accordance with traffic con ditions, all as explained above.

Contact finger 58 of relay CR alternately impresses a potential across first one part, and then another part, of the primary of transformer 58 by means of the wires 59 and Gil, and a center tap wire 6|, which passes through a contact finger 62 and front point of slow code relay 80R. This push-pull transformer arrangement is similar to that employed in the Hailes patent, referred to above, and produces a pulsating current in the secondary of transformer 58 having a frequency the same as that of the oscillations of relay CE.

The pulsating direct current from the secondary of transformer 58 passes to the primaries of two transformers 63 and as, by means of the wires 65 and 66; the circuit of the primary of transformer 63 being tuned by condensers 67, and the circuit of the primary of transformer 64 being tuned by condenser 83, to respectively be resonant, or substantially so, at a frequency of 120 per minute, and 180 per minute. manner, current sufficient to pick up, and hold up, the 180 rate relay 186R will pass through the relay only when the 180 code is on the track rails. Likewise, sufiicient current will flow through the 120 rate relay, to pick up, and hold up, relay iZtiR, only when alternating current coded at the rate of 120 per minute is in the track rails.

Each of the relays 129R and 38B has a repeater relay IEQRP, and ESERP, which are arranged to be slow to release, as by means of the employment of a short circuited copper winding of low resistance on its core, or in any other usual or desired manner. Each f these repeater relays is energized through a front point of its corresponding primary relay, and a back point of the other primary relay. With the parts as shown in the drawings, relay F8535. is picked up, since it is seen that 180 code is being received, and repeater relay IfiiiRP is picked up through a circuit including contact finger 6s and back point of IEBR, and contact finger Hi and front point of relay ISBR. The pick-up circuit for relay IZGRP is similar, and is obvious from the drawings.

The slow release characteristics of these repeater relays are desired for proper control of circuits to be described below, and it would appear sufficient, at the present point, to set forth that these slow release characteristics are built into repeater relays rather than into the primary relays IZUR and lsflR, in order to avoid decreasing the sensitivity of these primary relays which must respond relatively quickly to influences derived from the track rails.

The code relay CR. also includes a contact finger H, which follows the code, and which energizes a slow release front repeater relay CRFP, made slow to release by having bridged across its windings, a resistance 72. This makes the relay slow to release, without materially in- In this creasing its pick up time. This relay will thus pick up and stay up so long as contact finger H is vibrating at any of the three code rates.

Contact finger H, when making up its back point, puts energy on an energizing circuit for the relay R, this circuit including a contact finger 13 and front point of relay CRFP, and this relay 86R, like the relay CTFP, is made slow to release by means of a resistance 14 connected across its windings.

With this arrangement of circuits, it is clear that so long as relay CR oscillates its contact fingers, at a rate approaching 80 or over, the 80 code relay 80R will pick up and stay up. It will not, however, remain up if the relay CR fails to oscillate, since when CR is picked up, the energizing circuit for 3GB is broken at the back point of contact finger H, and after CR is released, the circuit is broken at the front point of contact finger 13.

Each of the tuning condensers 25, 29 and 32 have a shunt circuit connected across them, constituted, respectively, by the two wires, and contact finger and back point 15, i6 and Ti; 18, 79 and 80; and 8|, 82 and 83. The contact fingers T1, 80 and 83, which control these shunt circuits, and which, when in released position, shunt out the three corresponding condensers, and hence tune the receiving circuit for 100 cycle reception, are controlled by a check relay CRC. This relay is slow to release, due to a shunting resistance 84, in a manner similar to relay 80R, for example, and is energized through a circuit including contact finger H and back point of relay CR, and contact finger 85 and front point of a. system selecting relay SS.

In order that the receiving apparatus can properly respond to either of the two different trackway arrangements described above, this system selecting relay SS is employed, and can be energized by depressing a manually operable button PB, which preferably remains where placed, to thereby cause relay SS to pick up, through an obvious circuit. This completes the above traced energizing circuit for check relay CRC, whereby to open the three shunts across the three tuning condensers 26, 29 and 32, thereby to tune the receiving circuits for 140 cycle reception rather than for cycle reception.

Before considering the signal circuits, and the acknowledging circuits, it might simplify the explanation to first explain how the receiving and decoding apparatus responds to either the coded 100 cycle train control current, or the cycle noncoded train control current.

With the 100 cycle train control current on the track, and with the push button PB in its shown position, whereby relays SS and CRC are in released positions, and the shunts about the condensers are closed, the tuning is for 100 cycle reception. With code at the rate of per minute being received, relays |8E3RP and MR are picked up and held up; with code at the rate,

of 120 per minute being received, relays IZGRP and 85R. are picked up and held up, while IBBRP releases; and with code at the rate of 80 per minute both IZURP and ISSRP are released and only relay 89B is picked up. Of course, with no train control energy on the track rails, as exists when a train is in an occupied block, code relay OR is deenergized and all of the relays 80R, IEURP and I80RP are released in retracted positions.

If it is assumed the locomotive, tuned for 100 cycle reception as described above, should enter territory such as th blocks E -G, where 140 cycle train control current may be on the track, the receiving circuit, being untuned for this, will not receive the energy, and code relay CR will be released regardless of traffic conditions ahead. By reason of knowing the roadway, orby means of any desirable or suitable marker or indicator, the engineer wil1 know when he enters the 140 cycle territory and can then operate the push button PB. Upon the picking up of relay CRC, due to the push button being depressed, and the resulting tuning of the receiving circuits for 140 cycle reception, code relay CR will pick up, and in doing so will deenergize relay CRC, which will release and d'etune the receiving circuits and thus cause relay OR to release. This interplay between relay CR and CRC will repeat itself so long as 140 cycle energy is present in the track rails, and by proper adjustment of the timing of the relays involved, the code relay CR, can be caused to oscillate at any desired rate, and in thepresent instance, adjustments are made such that relay CR oscillates at the rate of approximately 189 times per minute, due to the steady reception by the car carried receivers of 140 cycle train control current.

Of course, even with the push button PB de pressed, if there be no train control energy in the 140 cycle territory, code relay CR will remain released, as is obvious.

Referring now to the acknowledging circuits, and the signal control circuits, there are here involved three acknowledging relays, a slow acknowledger, or SA, a low rate acknowledger, or LEA, and a medium rate acknowledger, or MBA. Also included is an acknowledging contact-or Aclc, which can be of the type shown in the Hailes patent, above identified, and which is biased by a spring, or the like, to the position shown in the drawing. When depressed by hand, it is operative to move the normal contact Bl and the reverse contact to, downwardly, to open the first, and to close the second.

The system is arranged to check the vigilance of the engineer, in somewhat the same manner as in the Hailes patent, above referred to, by causing a whistle valve WV, to sound, upon a change in traffic conditions from a more to a less, favorable character. The whistle valve continues to sound until a manual act is performed by the engineer, which act, in the present case, is that of depressing the acknowledging contactor.

The cab signals can assume various forms, but for the purpose of illustration, are here shown as a four aspect light signal, a G, or green signal, known as a clear signal, and indicating proceed at authorized speed; a Y/G, or yellow-green signal, known as an approach restricting signal, and indicating proceed at reduced speed; a Y, or yellow signal, known as an approach signal, and indicating approach at low speed; and a W, or white signal, known as a slow signal, and indicating proceed prepared to stop.

Considering now the acknowledging and signalling circuits more in detail, with the parts as shown in the drawings, the 180 code being received on the vehicle which is traveling in 100 cycle territory, the code relays SilR, and lSllRP are up, with the three acknowledging relays released, and the acknowledging contactor in its normal position. Under these conditions of travel, the whistle valve WV is energized through a circuit including contact finger 89 and front point of lStRP, contact finger 9t and back point of MBA, contact finger 9i and back point of LBA, contact finger 92 and back point of SA, the normal contact Bl and front point of Ack, and the whistle valve WV; whereby the whistle is silenced.

Also, under these conditions, the clear signal G, is energized through a circuit including contact finger 93 and back point of SA, contact finger es and front 'point of lSfiRP, and signal G.

We can now assume that, with the vehicle it remaining in block D, the vehicle 55 progresses and enters block B, whereby to receive cycle train control current coded at the rate of cycles per minute. After a short period of time, possibly two or three seconds, for the 583R? relay to release, the lliRl? relay is picked up through its energizing circuit, the energy received on the train causing the code relay OR to oscillate at the 120 rate whereby to send energy through the tuned circuit including transformer 63 so as to energize relay EZfiR. Thus, after a few seconds the condition is established of ldiiRP down, SEQRP up, and of course the relay fitR up, s nce this last relay is up for all of the codes.

Upon the release of relay scene the whistle valve becomes deenergized, and sounds, and in order to silence it, it is necessary that the engineer depress the acknowledging contactor Acic whereby to show that he is vigilant and recognizes that traflic conditions have become more restrictive.

Upon depressing Ack, a pick-up circuit is completed for acknowledging relay LRA which includes contact finger 89 on 58533? and back point, reverse contact 86 and back point of the acknowledging contactor, and the relay LRA.

The pickin up of relay LEA completes a pickup circuit for re acknowledging relay MBA which includes contact finger 39 and back point, contact finger 95 and front pointof LRA, and the relay MBA. Relay MBA is then stuck up through a circuit including contact finger 89 and back point, contact finger 85 and front point of relay contact finger 99 and front point of MBA, and relay MRA, thus making the stick circuit for MBA dependent upon the energized condition of the code repeater relay EZBRP.

The engineer, after acknowledging, will release the acknowledging contactor whereupon it will return to its normal position, thus opening the reverse contact 83 and breaking the pick-up circuit for relay LEA, which relay releases to break the pick up circuit for relay MBA, whereby the picked up condition of MBA is dependent solely upon ener ized condition of the medium rate, or EZQR'P relay.

With scene down and lfZilR-P and MBA up, an energizing circuit is completed for the whistle valve which includes contact finger 85 down, contact finger 25 up, contact finger il up, (contact finger it up), contact finger 9i of LRA down, etc, above explained.

With regard to the signal circuits under the condition now existing, the release of relay 585R]? deenergizes the G signal, and with lZ'fiRP up, the Y/G signal is energized through a circuit inclu ing contact finger 93 and back point, contact ringer and back point, contact finger 91 and front point of EEGRP, contact finger 98 and back 3-" int of r" "y 538, and signal Y/G.

in code to the so rate code, for as would be experienced by train 55 ng block C, with the following block D occupied, the code repeater relay lZtRP releases after a few seconds whereby to break the stick cuit for the whistle valve WV, as above explained, I

and of course, to break the energizing circuit for signal Y/G.

With relay 89R up, signal Y is energized through a circuit including contact finger 93 and back point, contact finger 94 and back point, contact finger 91 and back point, contact finger IOI and back point, contact finger I02 and front point of relay 80R, and signal Y.

Under the conditions assumed, the only one of the code relays which is up is the slow rate code relay 89R. In order to silence the whistle, the engineer must acknowledge, whereupon acknowledging relay LEA is picked up, as above, which causes the picking up of the acknowledging relay MRA, as above. In this case, however, instead of relay MRA being stuck up, relay LRA is stuck up through a circuit including contact finger 89 and back point, contact finger 96 and back point, contact finger 99 and front point of relay 80R, contact finger I and front point of LRA and relay LRA. Thus, upon the release of the acknowledging contactor, and the opening of the reverse acknowledging contact 88, the energization of relay LEA is dependent upon the energization of the code relay 80R. With LRA up, relay MBA is also up through its pick-up circuit, as traced above.

Under these conditions, the whistle valve is silenced, since it is energized through a circuit including contact finger 89 and back point, contact finger 96 and back point, contact finger 99 and front point, contact finger I00 and front point, contact finger 9I and front point, etc., as above.

Assuming now that the train enters the occupied block D, whereupon no code is received, the slow release code relay 89R, after a few seconds, releases its contacts, signal Y is deenergized, and signal W is energized through a circuit including contact finger 93 and back point, contact finger 94 and back point, contact finger 91 and back point, contact finger I93 and back point, and signal W.

Upon the release of code relay 89R, the energizing circuit for whistle valve WV is broken, and the stick circuit for acknowledging relay LEA is broken, which latter relay, upon releasing, causes the release of acknowledging relay MRA, due to the opening of contact finger 95. In order to silence the whistle valve, the engineer must manifest his vigilance by acknowledging, whereupon acknowledging relay SA is picked up through a circuit including contact finger 89 and back point, contactor 88 and back point, wires I04, I95, I95 and I91, contact finger I99 and back point of relay 89R, contact finger III! and back point of relay I2IJRP, contact finger III and back point of system selecting relay SS, wire H2, and relay SA.

On picking up, relay SA is stuck up through a circuit including contact finger 89 and back point, contact finger I I3 and front point, wires I I5 and I97, contact fingers I99, III! and III and their back points, wire I I2, and the relay SA.

With relay SA up, the acknowledging relays to the left thereof, that is, LRA and MBA are picked up through circuits which are obvious from the drawings, and include, in the case of relay LRA contact finger 89 and back point, and contact finger I I3 and front point; and in the case of MRA, contact finger 89 and back point, and contact finger 95 and front point.

With the acknowledging relay SA up, the whistle valve is energized through a circuit including contact finger 93 and front point of SA, wires II 6 and I I4, contact finger 92 and front point, normal contactor 81 of Ac lc, and the whistle valve WV; thus to silence the whistle valve.

Upon the release of relay 39R, signal Y becomes deenergized at contact finger I02 and front point; and the signal W becomes energized until acknowledged, through a circuit including con tact finger 93 and back point, contact finger 94 and back point, contact finger 9! and back point, contact finger I93 and back point, and signal W. Upon acknowledging, however, as explained above, which results in the picking up of acknowledging relay SA, energy is taken off of this circuit, but signal W is then energized through a circuit including contact finger 93 and front point, wires I I6, I I! and I I8, and signal W.

It is thus seen that upon any change of trafiic conditions from a less restrictive to a more re strictive character, the whistle valve WV sounds, and checks the vigilance of the engineer, since it is necessary to perform the manual act of acknowledging, in order to silence this Whistle valve.

On a change, however, from more restrictive to less restrictive conditions, no acknowledgment is necessary, since the whistle valve does not become deenergized at all, unless it is very fast acting, whereupon it is only momentarily deenergized, as will'be explained below.

Assume, for example, that the train is proceeding in a danger block, with signal W energized, with all of the three acknowledging relays MRA, LRA and SA up, and the three code relays R, I20RP and I89RP down; and that conditions clear up so that coded cycle current is received at a rate, for example, of 80 per minute. The code relay 89R, will pick up, as is obvious from the above explanation. The picking up of relay 89R. breaks the stick circuit for acknowledging relay SA, at contact finger I09 and back point of relay 80R. After a short period of time, such as two or three seconds, relay SA releases, to thereby break the energizing circuit for the whistle valve, and the energizing circuit for the signal W, at contact finger 93 and front point, but on making up its back point, the circuit is completed for energizing the signal Y, as traced above, whereby the signal changes from W to Y, upon a change of code as assumed above, provided the code persists several seconds, that is, persists a sufficient time to cover the release time of relay SA. This feature is desirable in order to avoid clearing up a stop signal, due to an accidental or temporary interruption of danger conditions, and assures that the engineer is not relieved of a slow signal unless a less restrictive condition persists for an appreciable time.

The release of relay SA, also, as set forth above, breaks the energizing circuit for whistle valve WV, but acknowledging relay LRA which must be up under the 80 code rate to silence the whistle, is already up, and upon the picking up of relay 80R, this acknowledging relay LRA becomes stuck up through its stick circuit, as traced above, whereby to hold up acknowledging relay MRA to its left, and to complete an energizing circuit for the whistle valve WV, as traced above, which circuit includes contact finger 92 and back point of relay SA. 7

Thus, the shift from one energizing circuit to the other for the whistle valve comprises a shift in the contact fingers of relay SA from front to back points, and during this operation of the relay the whistle valve is deenergized. If the whistle valve be made slightly slow acting, it will'not sound during this momentary deenergization, while if it is made quick acting, it will give only a very short blast during this momentary deenergization. It is contemplated in some systems to make the whistle slow acting whereby there-is no whistle blast on such a change to less restrictive conditions. Itis also contemplated, under certain conditions, to make the whistle valve fast acting, whereby to give a short blast'upon such a change in traiiic conditions whereby to apprise the engineer that the signal has changed, and since the whistle automatically ceases sounding after a very short period, to indicate thereby that the change is towards a more favorable condition.

In the same manner, it can be seen that a change from the 80 code rate, to the 120 code rate; and from the 120 code rate, to the 180 code rate;. results either in no whistle blast whatsoever, or a very short blast, according as the whistle be slow acting or fast acting. Also acknowledgment is not necessary, because, on a change from the 80 to the 120 rate, although the stick circuit'for acknowledging relay LEA is broken at contact finger 99 and front point of can, the acknowledging'relay MBA, which is already up at the time of the change, will become stuck up through the stick circuit traced above. In a similar manner, though the stick circuit for MBA is broken upon the release of IZURP, with libRP up,- a new energizing circuit for the whistle valve is established, as traced above.

As set forth above, relay SA is made slow acting, and the signal W is energized through a front point thereof, whereupon signal W persists for the; period of the release time of relay SA after more favorable traffic conditions have taken place. In other words, the signal W is made dependent upon slow release acknowledging relay SA. This should be kept in mind since, in the following discussion of acknowledgment in the non-coded territory, where the 140 cycle train control current is employed, the signal W is notmade dependent upon slow release acknowledging relay SA; but is made dependent upon quick release acknowledging relay LRA,

7 whereby to assure proper cooperation with the acknowledging loops IT, as will appear more clearly frointhe below explanation.

Assume now that a train proceeding, for example, under the 180 code, shall enter the non-coded territory, that is, shall enter block E, for example, in an east bound direction. If the train onters the non-coded territory, the engineer will ordinarily be properly advised of the same, and

expected to operate his push button PB, although he may or may not do so.

We will assume first that the push button PE is operated upon the entry into the non-coded territory, whereupon the receiving circuits are tuned to receive 140 cycle current, due to relav CRO being picked up, as explained above. Upon relay CR responding to the incoming energy, the energizing circuit for CRC is broken, as described above, whereby relay CR oscillates at substantially .same rate as if the 100 cycle current, coded at the 180 rate, were being received. In such circumstances, code relays 89R. and 139B? pick up exactly as described in connection with operand relay CR releases again,

ation in the coded territory under 180 code, and no change is encountered in the signal aspects.

, The signal G remains energized, as it should,

but

since, although the train has passed from one territory to the other, it has passed from proceed conditions in one territory to proceed conditions in the other territory. The acknowledging loops I? make no difference, in the conditions assumed, since, when the rails are energized with 140 cycle current, the rails and the loops are the same with regard to their influences on the locomotive equipment.

If we now assume that, upon entry into the block E, from the block D, running under a G signal, the engineer fails to push the button PB, then the receiving circuit is not tuned for 140 cycle current, and accordingly, both code relays iitR and EGFERP release, to thus energize signal W through a circuit including contact fingers 93, 94, 9? and 553 and their back points.

The release of relay 539R? br aks the enercircuit for whistle WV, at contact finger 39 and front point, and accordingly, in order to silence the whistle, the engineer must manifest his vigilance by operating the acknowledging contactor.

Assuming that a train enters E with PB depressed and an advance train is in E, upon acknowledging, it is not acknowledging relay SA which is stuck up, as was the case under like conditions in coded territory, but it is the acknowledging relay next to the left thereof, namely, relay LRA, which is first picked up, through a circuit including contact iinger 88 and back point, and acknowledging contactor 8 3 and back point, as described above, and then stuck up through a circuit including contact finger 68 and back point, contact finger H3 and front point, of system selecting relay SS, wire 2%, contact finger see and front point, and relay LEA.

The picking up of relay LRA completes an energizing circuit for the whistle valve WV which includes contact finger 39 and back point, contact finger H9 and front point, wire I28; contact finger his front point, contact finger el and front point, contact finger 92 and back point, the acknowledging contactor 5i and front point, and the whistle valve WV.

It can be seen from the above, that the circuit for energizing the whistle valve is dependent upon the quick release acknowledging relay LRA, in the case of non-coded territory, and not upon the slow release acknowledging relay SA, as was the case in coded territory. Also, on acknowledging, upon receiving a slow indication, due to the system selecting relay SS being up, it is the acknowledging relay LRA rather than .SA which is picked up and stuck up.

Upon the train entering the next block, such as F, the acknowledging loop W is encountered, and regardless of whether or not this block is occupied, or in other words, regardless of whether or not this block is a danger or a clear block, the train, while passing over the loop, will receive stead current of a frequency of 140 cycles, and acc ly, during this time, the code relays psi-1P will pick up and stay up. This signal to G. and the picking up of erses block after block, if clear, under a proceed signal G, without any change in the apparatus on the locomotive.

On leaving the loop I1 if the block F or block G be occupied, however, the receiving circuits are deprived of energy and code relays 80R and I80RP release, whereby to deenergize the whistle valve and cause it to sound and thus require the acknowledging act in order to silence it, as set forth above,

The time required by the fastest train to pass over the acknowledging loop, is greater than the release time for the acknowledging relay LRA, whereby a train, upon leaving the loop, and. encountering stop conditions, will be under the neoessity of acknowledging in order to silence the whistle valve. If the whistle valve should be under the control of the slow release relay SA, and if the time for traversing the acknowledging loop by the fastest train should be less than the release time of relay SA, even though the acknowledging loop should result in the picking up of relays 80R and I80RP, and hence, the deenergization of relay SA, the relay SA would not have released at the time the train left the loop, and hence, the whistle would not have sounded and thus required acknowledgment.

A moments consideration of the two trackway apparatuses involved will show that in the coded territory, if one train is following a forward train and is in the same block, it receives no code, and the cab signal is W or slow. This signal, however, cannot continue from block to block, because the forward train must leave any particular block before the rear train does and hence give the rear train at least an 80 code, whereby to change the signal to proceed or G, so that, upon again entering occupied territory, acknowledgment will be enforced.

In the non-coded territory, however, restricted conditions are encountered both in an occupied block and in the block to the rear of an occupied block, and hence, two trains spaced from each other by approximately one block length, and traveling at the same speed, could result in continuing restricted conditions on the rear train as it travelled from block to block. In such circumstances, the engineer might well become accustomed to the stop signal, and relax his vigilance in view thereof. In order to avoid any such condition existing, the acknowledging loops I! are employed, whereby, at the entrance to each block in non-coded territory, the signal is temporarily moved away from a slow signal, if such be in force, and then moved back again, if danger conditions exist, whereby to enforce acknowledgment near the entrance end of each danger block.

With the apparatus as described above, it can be seen that locomotive apparatus has been provided which can be changed over by means of a manually operable switch to equally well coact with either of two quite different forms of trackway apparatus.

Furthermore, acknowledgment has been provided for in which substantially the same appara tus is employed in the case of both of the trackway apparatus, and likewise is it the case with the signal circuits and signals. Also, the receiving and filtering and amplifying apparatus is substantially the same in both cases, with very little addition of parts to set the locomotive apparatus to cooperate with the different forms of trackway apparatus.

In short, apparatus has been provided which responds to coded 100 cycle current, and which responds to non-coded cycle current in a manner in effect, to code the 140 cycle current by means of the locomotive equipment, whereby the decoding apparatus need respond only to coded energy.

The above rather specific description of one form which the present invention can assume, has been given solely by way of example, and is not intended, in any manner whatsoever, in a limiting sense. It is to be understood that all such modifications and substitutions as may occur from time to time, in the kind and arrangement of parts disclosed, are intended to be covered by the present application, insofar as they are not specifically excluded therefrom by the reasonable interpretation of the appended claims.

Having described my invention, I new claim:

1. In train control systems, in combination with a first stretch of track divided into isolated blocks and having means for placing variously coded train control alternating current of a first frequency on the rails in accordance with traific conditions ahead, and a second stretch of track divided into isolated blocks and having means for placing non-coded train control alternating current of a second and different frequency on the track rails in accordance with traffic conditions ahead, car carried apparatus including a receiving circuit, a plural aspect cab signal, control means for causing the signal to display distinctive aspects in accordance with traffic conditions ahead and means including the signal control means for tuning the circuit to resonance at either the first, or the second, frequency.

2. In train control systems, in combination with a first stretch of track divided into isolated blocks and having means for placing variously coded train control alternating current of a first frequency on the rails in accordance with traffic conditions ahead, and a second stretch of track divided into isolated blocks and having means for placing non-coded train control alternating current of a second and different frequency on the track rails in accordance with traffic conditions ahead, car carried apparatus including, a receiving circuit, a plural aspect cab signal, a decoding circuit for controlling the signal in accordance with trafiic conditions ahead, code following means for intermittently energizing the decoding circuit at a rate proportional to the coded current received from the rails, and means including said code following means, for selectively tuning the receiving circuit for one or the other of said frequencies.

3. In train control systems, in combination with a first stretch of track divided into isolated blocks and having means for placing variously coded train control alternating current of a first frequency on the rails in accordance with traffic conditions ahead, and a second stretch of track divided into isolated blocks and having means for placing non-coded train control alternating current of a second and different frequency on the track rails in accordance with trafiic conditions ahead, car carried apparatus including, a receiving circuit, a plural aspect cab signal, a decoding circuit for controlling the signal in accordance with trafiic conditions ahead, code following means for intermittently energizing the decoding circuit at a rate proportional to the coded current received from the rails, means including said code following means, for

selectively tuning the receiving circuit for one or the other of said frequencies, and means when the receiving circuit is tuned to the second frequency, and responsive to steadily applied alternating current in. the rails, to intermittently energize thedecoding circuit at substantially the same rate as if the car were receiving one of the codes from the first stretch of tr sin 4.111 train control systems, in combination with a first stretch of track divided into isolated blocks and having for placing variously coded train control alternating current of a first frequency on the rails in accordance with trafiic conditions ahead, and a second stretch of track divided into isolated blocks and having means for placing non-coded train control alternatingcurrent of asecond and different fr; quency on the track rails in accordance with traffic conditions ahead, car carried apparatus including, a receiving circuit, a plural aspect cab signal, a decoding circuit for controlling the signal in accordance with trafiic conditions a normally cleenergized code following relay means picked up only when energized and released when deenergized for intermittently energising the decoding circuit at a rate in accordance with the rate of code of th coded current received fromthe rails, means for manually selectively tuning thereceiving circuit for one or the other of said frequencies, and means including said code following relay means and the tuning means, when the receiving circuit is manually tuned to the second frequency and respol sive to non-coded alternating current in the rails, to intermittently energize the decod ng circuit at the same rate as if the car were receiving one of the codes from the first stretch of track.

5. In train control systems, in combination with a first stretch of track divided into isolated blocks and having means for placing variously coded train control alternating current of a first frequency on the rails in accordance with traific conditions ahead, and a second stretch of track divided into isolated blocks and having means for placing non-coded train control alternating current of a second and different frequency on the track rails in accordance with traffic conditions ahead, car carried apparatus including, a receiving circuit, a plural aspect cab signal, a decoding circuit for controlling the signal in accordance with traihc conditions ahead, code following means for intermittently energizingthe decoding circuit at a rate proportional to the code rate of the coded current received from the rails, means for selectively tuning the receiving circuit for one or the other of said frequencies, means, when the receiving circuit is tuned to the second frequency, responsive to uninterrupted. alternating current in the rails, to intermittently energize the decoding circuit at the same rate as if the car w re receiving one of the codes from the first stretch of track, a whistle, acknowledging circuit means for making the whistle sound upon every change in trafiic conditions to more restrictive in either stretch of track, and a manual contactor operable to silence the whistle, the second stretch or track having means at the entrance end of each block for always supplyingthe car with alternating train control current regardless of traific conditionsto thereby enforce recurrent acknowledgment.

6. In train control systems, in combination with a first stretch of track divided'into isolates blocks and having means for placing variously coded train control alternating current of a firs frequency on the rails in accordance with traffic conditions ahead, and a second stretch of track divided into isolated blocks and having means for-placing non-coded train control alternating current of a second and different frequency on the track rails in accordance with traflic conditions ahead, car carried apparatus including, a receiving circuit, a plural aspect cab signal, a decoding circuit for controlling the signal in accordance with trafiic conditions ahead, code following means for intermittently energizing the decoding circuit at a rate dependent on the code rate of the coded current received from the rails, means for selectively tuning the receiving circuit for one or the other of said requencies, means when the receiving cil cult is tuned to the second frequency, and responsive to steadily applied alternating current in the rails, to intermittently energize the decoding circuit atthe same rate as if the car were receiving one of the codes from the first stretch of track, a whistle, acknowledging circuit means for making the whistle sound upon every change in traific conditions to more restrictive in either stretch of track, a manual conta'ctor operable to silence the whistle, the second stretch of track having means at the entrance end of each block for always supplying the car with alternating train control current regardless of trafiic conditions ahead to thereby enforce recurrent acknowledgment, the acknowledging circuit means including a slow release relay and a quick release relay, and an energizing circuit for the whistle including a front point of the slow release relay and completed upon acknowledging a change in the first stretch of track to a more restrictive signal aspect, and an energizing circuit for the whistle valve includ ing a front point of the quick release relay and completed upon acknowledging a change in the second stretch of track to a more restrictive signal aspect. v

7. 'In a train control system, in combination, car carried apparatus including, a receiver for receiving energy from track rails, a receiving circuit, connected to the receiver, and tuned to resonance at a first frequency, a normally deenergized 'code following relay connected in the receiving circuit and picked up only when energized, a cab signal having a plurality of aspects, control circuits for said signal controlled by said code following relay, a selecting relay, an energizing circuit for the sel cting relay controlled by said code following relay, and circuit means controlled by the selecting relay, when energized, to tune the receiving circuit to resonance at a second and different frequency.

8. In a train control system, in combination, car carried apparatus including, a receiver for receiving energy from track rails, a receiving circuit, connected to the receiver, and tuned to resonance at a first frequency, a selecting relay, circuit means controlled by the selecting relay, when energized, to tune the receiving circuit to resonanceat a second and different frequency, a normally deenergized code following relay connected to the receiving circuit, a cab signal having a plurality of aspects, signal control circuits con trolled by said code following relay, the energizing circuit for the selecting relay including a back point of the code following relay whereby energy of the second frequency and steadily received causes the code following relay to oscillate.

9. in a train control system, a first stretch 01 track divided into isolated blocks, means to apply to said stretch alternating current of a first frequency coded at one of three rates, or to not apply it, all in accordance with traffic conditions,

a second stretch of track divided into isolated blocks, means to either steadily apply alternating current of a second and different frequency, or to not apply it, to the second stretch in accordance with traffic conditions, and car carried apparatus including a receiver circuit, means to tune the circuit at will for either of said frequencies, a four aspect signal, and signal circuit means controlled by the receiver circuit to give any one of the four aspects when in the first stretch of track, and any one of two of the four aspects when in the second stretch of track.

10. In a train control system, a first stretch of track divided into isolated blocks, means to apply alternating current of a first frequency coded at one of three rates, or to not apply it, to said blocks, all in accordance with trafiic conditions, a second stretch of track divided into isolated blocks, means to either steadily apply alternating current of a second and different frequency, or to not apply it, to the second stretch in accordance with traffic conditions, car carried apparatus including a receiver circuit, means to tune the circuit, at will, for either of said frequencies, a cab signal having four aspects of varying restrictivenesses, and signal circuit means controlled by the receiver circuit to energize any one of the four aspects when in the first stretch of track, and either the most, or the least, restrictive of the four aspects when in the second stretch of track. I

11. In train control systems, in combination with a first stretch of track divided into isolated blocks and having means for placing variously coded train control alternating current of a first frequency on the rails in accordance with traffic conditions ahead, and a second stretch of track divided into isolated blocks and having means for placing non-coded train control alternating current of a second and different frequency on the track rails in accordance with traffic conditions ahead, car carried apparatus including a receiving circuit, manually operable means for tuning the circuit to resonance at either the first, or the second, frequency, a plural aspect cab signal, signal control means for causing the signal to display its least restrictive indication when the receiving circuit is effectively energized with said non-coded current, and to display its most restrictive indication when the receiver is effectively energized by non-coded current of the first frequency regardless of the 'tuning of the receiving circuit.

12. In train control systems, in combination with a first stretch of track divided into isolated blocks and having means for placing variously coded train control alternating current of a first frequency on the rails in accordance with traific conditions ahead, and a second stretch of track divided into isolated blocks and having means for placing non-coded train control alternating current of a second and difierent frequency on the track rails in accordance with traific conditions ahead, car carried apparatus including a receiving circuit, manually controllable means for tuning the circuit to resonance at either the first, or the second frequency, a plural aspect cab signal, and control means for causing the signal to display distinctive aspects in accordance with the existing train control current, said control means including a code relay responsive to control energy in the receiver to pick up, and to the absence of control energy in the receiver, to release the tuning means, when manually controlled, tuning the receiving circuit for the noncoded current only when the code relay is released, and for the coded current when the code relay is picked up, and signal control means causing the signal to display its most restrictive indication when the code relay remains up.

13. In train control systems, in combination with a first stretch of track divided into isolated blocks and having means for placing variously coded train control alternating current of a first frequency on the rails in accordance with traffic conditions ahead, and a second stretch of track divided into isolated blocks and having means for placing non-coded train control alternating current of a second and different frequency on the track rails in accordance with trafiic conditions ahead, car carried apparatus including a receiving circuit, manually controllable means for tuning the circuit to resonance at either the first, or the second frequency, a plural aspect cab signal, and control means for causing the signal to display distinctive aspects in accordance with the existing train control current, said control means including a code relay responsive to control energy in the receiver to pick up, and to the absence of control energy in the receiver, to release the tuning means, when manually controlled, tuning the receiving circuit for the non-coded current only when the code relay is released, and

for the coded current when the code relay is picked up, the signal control means causing the signal to display its most restrictive indication when the code relay remains up, and to display its least restrictive indication when the receiving circuit is energized by coded current of one rate, and also when energized by non-coded current and the tuning means is in operated position.

14. In train control systems, in combination with a first stretch of track divided into isolated blocks and having means for placing variously coded train control alternating current of a first frequency on the rails in accordance with trafiic conditions ahead, and a second stretch of track divided into isolated blocks and having means for placing non-coded train control alternating current of a second and different frequency on the track rails in accordance with trafiic conditions ahead, car carried apparatus including a receiving circuit, a code following relay energized through the receiving circuit, manually controllable means dependent for its control on the code following relay for tuning the circuit to resonance at either the first, or the second, frequency, a plural aspect cab signal, signal control means including the code following relay for causing the signal to display its least restrictive indication when the receiving circuit is effectively energized with saidnon-coded current, and to display its most restrictive indication when the receiver is effectively energized by non-coded current of the first frequency regardless of the tuning of the receiving circuit.

, 15. Ina train control system, in combination, car carried apparatus including, a receiver for receiving energy from track rails, a receiving circuit, connected to the receiver, and tuned to resonance at a first frequency, a manually controllable selecting relay, circuit means controlled by the selecting relay, when energized, to tune the receiving circuit to resonance at a second and different frequency, a normally deenergized code following relay connected to the receiving circuit, a cab signal having a plurality of aspects, signal control circuits controlled by said code following relay, the energizing circuit for the selecting relay including a back point of the code plifier and responsive only ii following relay whereby energy of the second frequency and steadily received causes the code following relay to oscillate, and whereby energization of the selecting relay when under the influence of current of the first frequency if steadily received causes the code following relay to pick up and stay up, the said signal control circuits producing the most restrictive indication when the code following relay is stationary.

16. In a cab signalling system, the combination with a car-carried receiver inductively coupled with the track rails for receiving coded energy of one frequency or uncoded energy of another frequency from the track rails, an amplifier, a cab signal, circuit means connecting said receiver and said amplifier and tuned to pass energy of said one frequency, governing means for controlling said cab signal and controlled by said amcoded energy is delivered by said amplifier, electro-responsive means controlled in part by said governing means for changing the tuning of said circuit means, and means including said governing means controlled by said amplifier for intermittently actuating said electro-responsive means to intermittently change said tuning only if the energy supplied from said receiver to said amplifier is of said another frequency, the current received by said amplifier being above a predetermined value to actuate said electro-responsive means when said circuit means is tuned to said another frequency and being below such predetermined value to allow dropping of said electro-responsive means when said circuit means is tuned to said one frequency to thereby cause intermittent actuation of said electro-responsive means.

17. In a cab signal system, a car-carried receiver inductively coupled with the track rails,

code following relay means on the'car, a circuit tuned to a particular frequency for transmitting current from said receiver to said code following relay means, a signal, decoding means controlled by said code following relay means for rendering said signal effective only if said code following relay means operates intermittently to characterize a particular code, a relay for changing the tuning of said circuit, manually controlled means for controlling said relay and tuning said circuit to a different frequency, and a contact controlled by said code following relay means and operated intermittently in accordance with the intermittent operation of said code following relay means for controlling said relay, whereby if said manually controlled means is operated and non-coded current of said different frequency is flowing in the track rails said code followingfrelay means will be intermittently op-' erated through the medium of said relay and said relay-means will be intermittently operated by said relay through the medium of said tuning means.

18. In combination, a receiver supported in 7 front of the first axle of arailway vehicle and inductively coupled to the track circuit directly ahead of said vehicle, an amplifier on the vehicle,

[circuit means including a tuned filter permitting ready flow of alternating current of a first frequency and connecting said receiver and amplifier, manually controlled means for tuning said filter to permit the ready flow of alternating current of a second frequency, and, means including said manually controlled means and effective only when said manually controlled means is in its active condition and controlled by the out-put circuit of said amplifier toretunesaidfilter back i to perm-it ready fiow of alternating current of said first frequency for a time following th reception of alternating current of said second frequency only at the in-put circuit of said amplifier, whereby said circuit means is intermittently de-tuned when alternating current of said second frequency fiows in said track circuit with fier, electro-responsive means connected to the out-put circuit of said amplifier and having a biased closed contact, a manually controlled contact means, a relay, an energizing circuit for said relay including said biased closed contact and a contact of said contact means closed when said contact means has been manually controlled,-

contacts controlled by said relay to tune said filter to permit the ready fiow of alternating current of a second frequency when said relay filter to permit the ready fiow of alternating current of a second frequency, electro-responsivemeans controlled by the out-put circuit of said amplifier and having a contact closed when such electro-responsive means is deenergized, and means including said manually controlled means and controlled by said contact to retune said filter to permit the ready flow of alternating current of said first frequency when such electroresponsive means is energized, whereby with said manually controlled means operated and upon th flow of current of said second frequency in the track rails of sufficient magnitude to cause energization of said electro-responsive device when said filter is tuned to permit ready fiow of alternating current of the escond frequency but of insufficient magnitude to cause energization of said electro-responsive means when said filter is tuned to permit the ready fiow of alternating current of said first frequency said electro-responsive means will be intermittently energized.

21. In combination, a' receiver supported in front of the first axle of a railway Vehicle and inductively coupled to the track circuit directly ahead of said vehicle, an amplifier on the vehicle,

circuit means including a tuned filter permitting I read-y ficw of alternating current of a first frequency and connecting said receiver and amplifier, manually controlled means for tuning said filter to permit the ready flow of alternating current of a second frequency, electro-responsive means controlledby the out-put circuit of said amplifier and having a contact closed when such electro-responsive means is deenergized, means including said manually controlled means and controlled by said contact to retune said filter to permit the ready flow of alternating current of said first frequency when such electro-responsive means is energized, whereby with said manually controlled means operated and upon the fiow of current of said second frequency in the track rails of sufiicient magnitude to cause energization of said electro-responsive device when said filter is tuned to permit ready fiow of alternating current of the second frequency but of insufficient magnitude to cause energization of said electro-responsive means when said filter is tuned to permit the ready flow of alternating current of said first frequency said electro-responsive means will be intermittently energized, and code responsive means controlled by said electro-responsive means effective only if said electro-responsive means is intermittently energized.

22. In combination, car-carried apparatu including a receiver supported in front of the first axle of the car and inductively coupled with the track rails, an amplifier, a circuit connecting said receiver to the input circuit of said amplifier and including a filter tuned to pass alternating current of a first frequency, a main relay normally assuming a deenergized condition connected to be energized from the out-put circuit of said amplifier, a second relay, a manually controlled contact, a circuit for said second relay including a contact of said main relay and said manually controlled contact when in its actuated position, and contacts controlled by said second relay for at times tuning said filter to pass alternating current of a second frequency.

23. In combination, car-carried apparatu including a receiver supported in front of the first axle of the car and inductively coupled with the track rails, an amplifier, a circuit connecting said receiver to the input circuit of said amplifier and including a filter tuned to pass alternating current of a first frequency, a main relay normally assuming a deenergized condition connected to be energized from the out-put circuit of said amplifier, a second relay, a manually controlled contact, a circuit for said second relay including a back contact of said main relay and said manually controlled contact when in its actuated position, and contacts controlled by said second relay for tuning said filter to pass alternating current of a second frequency when said second relay is in its energized condition.

24. In combination, a receiver mounted ahead of the first axle of a car and in inductive relation with the track rails, an amplifier, a circuit including a filter normally tuned to pass alternating current of one frequency connecting said receiver to the input side of said amplifier, a manually controlled means for when actuated tuning said filter to pass alternating current of a second frequency, and means effective, when said manually controlled means is actuated, for tuning said filter back to passing alternating current of said one frequency and controlled by current flowing in the out-put circuit of said amplifier and efi'ective each time said amplifier delivers energy above a predetermined value, whereby said filter is alternately tuned from said second frequency and to said one frequency if continuous alternating current of said second frequency fiows in said track rails.

25. In combination, a receiver mounted ahead of the first axle of a car and in inductive relation with the track rails, an amplifier, a circuit including a filter normally tuned to pass alternating current of one frequency connecting said receiver to the input side of said amplifier, manually controlled means for when actuated tuning said filter to pass alternating current of a second frequency, means effective when said manually controlled means is in its actuated condition for tuning said filter back to passing alternating current of said one frequency in response to current flowing in the out-put circuit of said amplifier and effective each time said amplifier delivers energy above a predetermined value, whereby said filter is alternately tuned from said second frequency and to said one frequency if continuous alternating current of said second frequency flows in said track rails, and a signal on the car also controlled in accordance with the energy delivered by said amplifier and rendered effective only if such energy is delivered intermittently.

26. In combination, a receiver mounted ahead of the first axle of a car and in inductive relation with the track rails, an amplifier, circuit means including a filter normally tuned to pass alternating current of one frequency connecting said receiver to the input side of said amplifier,

manually controlled means for when actuated tuning said filter to pass alternating current of a second frequency, and means effective when said manually controlled means is in its actuated condition for tuning said filter back to passing alternating current of said one frequency in response to current flowing in the output circuit of said amplifier and effective each time said amplifier delivers energy above a predetermined value, whereby said filter is alternately tuned to said one frequency and to said second frequency if continuous alternating current of said second frequency flows in said track rails.

27. In combination, a receiver mounted ahead of the first axle of a car and in inductive relation with the track rails, an amplifier, circuit means including a filter normally tuned to pass alternating current of one frequency connecting said receiver to the input side of said amplifier, manually controlled means for when actuated tuning said filter to pass alternating current of a second frequency, means effective when said manually controlled means is in its actuated condition for tuning said filter back topassing alternating current of said one frequency in response to current fiowing in the output circuit of said amplifier and effective each time said amplifier delivers energy above a predetermined value, whereby said filter is alternately tuned to said one frequency and to said second frequency if continuous alternating current of said second frequency flows in said track rails, and a signal on the car also controlled in accordance with the energy delivered by said amplifier and rendered effective only if such energy is delivered intermittently.

28. In combination, a receiver supported in front of the first axle of a. railway vehicle and inductively coupled to the track circuit directly ahead of said vehicle, an amplifier on the vehicle, an electro-responsive device, circuit means including a tuned filter tuned to pass alternating current of a first frequency and including back contacts of said electro-responsive device, and

connecting said receiver to the input circuit of said amplifier, a rectifier, a main relay energizable from the output circuit of said amplifier through the medium of said rectifier, supplemental tuning means for tuning said filter to pass alternating current of a second frequency and eifective when said back contacts are open, a manually controlled contact, and a circuit for said electro-responsive device including a back contact of said main relay and said manually controlled contact.

29. In combination, a receiver supported in front of the first axle of a railway'vehicle and inductively coupled to the track circuit directly ahead of said vehicle, an amplifier on the vehicle, an electro-responsive device, circuit means including a tuned filter tuned to pass alternating current of a first frequency and including back contacts of said electro-responsive device and connecting said receiver to the input circuit of said amplifier, a rectifier, a main relay energizable from the output circuit of said amplifier through the medium of said rectifier, supplemental tuning means for tuning said filter to pass alternating current of a second frequency and effective when said back contacts are open, a manually controlled contact, a circuit for said electro-responsive device including a back contact of said main relay and said manually controlled contact, and code responsive means on the vehicle rendered effective only if said main relay is intermittently energized.

WADE H. REICHARD. 

